Heretofore, non-solvent-type moisture curable adhesives containing an isocyanate group-terminated urethane prepolymer as a main component have been known. Furthermore, as one kind of this type of the adhesives, there is known a hot-melt-type moisture curable adhesive (hereinafter also simply referred to as “reactive hot-melt adhesive”) which is paste or solid at room temperature and has the property of melting at the time when heated. The reactive hot-melt adhesive has characteristics that, in the case that substrates are coated with the adhesive melted by heating and the substrates are adhered each other, such an initial adhesive force that can fix the substrates each other is generated by cooling and solidifying the adhesive, the substrates are hardly shifted each other, and thereafter, a strong adhesive force can be exhibited by moisture curing of the adhesive.
Moreover, in the case that adhesion of textile products is purposed in clothing applications and the like, it is required for the reactive hot-melt adhesive that workability is excellent in the step of melting the reactive hot-melt adhesive and applying it to substrates (e.g., viscosity of the reactive hot-melt adhesive when melted (melt viscosity) is an appropriate value and such an initial adhesive force that the substrates are hardly shifted each other can be exhibited), the adhered part is excellent in sweat-deterioration resistance and hydrolysis resistance, and a touch and a feel of the adhered textile products, i.e., texture as clothing, are good.
As reactive hot-melt adhesives using a polyester polyol as the raw material, there are heretofore known (a1) an adhesive using a urethane prepolymer obtainable by reacting a high-molecular-weight (about 4,000 to about 11,000) polyester diol with a polyisocyanate compound, as a reactive hot-melt adhesive for clothing using an isocyanate group-terminated urethane prepolymer (e.g., see Patent Document 1); (a2) an adhesive using a urethane prepolymer obtainable by reacting a polyester diol having a hydroxyl value-converted average molecular weight of about 700 to 2,500 and a polyester diol having a hydroxyl value-converted average molecular weight of about 1,000 to 3,500 with a polyisocyanate compound (e.g., see Patent Document 2); (a3) an adhesive using a urethane prepolymer obtainable by reacting a crystalline polyester diol having a hydroxyl value-converted average molecular weight of 3,000 to 10,000 and a crystalline polyester diol having a hydroxyl value-converted average molecular weight of 1,000 to 3,000 with a polyisocyanate compound (e.g., see Patent Document 3); and (a4) an adhesive using a prepolymer obtainable by reacting a crystalline polyester diol with a polyisocyanate compound and further reacting the resulting isocyanate group-terminated urethane prepolymer with a low-molecular-weight diol (e.g., see Patent Document 4).
Moreover, as the adhesives obtained using a polycarbonate polyol as a raw material, there are heretofore known (b1) a reactive hot-melt adhesive comprising a combination of a polycarbonate-based urethane prepolymer and a saturated polyester resin (e.g., see Patent Document 5); (b2) a moisture curable adhesive obtainable by forming an isocyanate group-terminated urethane prepolymer using a specific polycarbonate polyol as a raw material and further reacting the resulting prepolymer with a low-molecular-weight diol or diamine, as an adhesive having improved deterioration resistance against oleic acid (this is referred to as sweat-deterioration resistance) and hydrolysis resistance against an aqueous lactic acid solution (e.g., see Patent Document 6); and (b3) a non-solvent-type moisture curable hot-melt urethane resin composition comprising a urethane polymer wherein content of a polycarbonate polyol in whole polyol components is 20% by weight or more, an amine-based catalyst, and water (e.g., see Patent Document 7).
Patent Document 1: JP-A-11-256131 (U.S. Pat. No. 5,939,488)
Patent Document 2: JP-A-62-181375
Patent Document 3: JP-A-7-118622
Patent Document 4: JP-A-6-271832
Patent Document 5: JP-B-7-17891
Patent Document 6: JP-A-2003-313531
Patent Document 7: JP-A-2003-246830
The adhesive of the above-mentioned (a1) has a characteristic of a fast solidifying speed but the melt viscosity is high and the workability is not sufficiently good. Moreover, the adhesive of the above-mentioned (a2) is excellent in flexibility and elasticity after curing and the resulting texture obtained when the fabrics and the like are adhered is good but the workability is not sufficiently good due to high melt viscosity. Furthermore, the adhesive of the above-mentioned (a3) is an adhesive for soft vinyl chloride resin sheets having low thermal resistance and is not necessarily suitable for use in textile substrates. The adhesive of the above-mentioned (a4) exhibits a high adhesive force at the initial stage of curing but has a disadvantage that, when the isocyanate group-terminated urethane prepolymer is reacted with a low-molecular-weight diol, the urethane prepolymer solidifies and then is not melted in some cases and, even when it can be melted, temperature for melting should be elevated to extremely high temperature. In addition, reactive hot-melt adhesives using these known isocyanate group-terminated polyester-based urethane prepolymers are insufficient in deterioration resistance against oleic acid (sweat-deterioration resistance) and hydrolysis resistance against an aqueous lactic acid solution.
Moreover, the adhesive of the above-mentioned (b1) is excellent in moisture resistance (hydrolysis resistance) and adhesiveness but heating and melting at high temperature are necessary in order to control viscosity to a value capable of easily coating on the substrates, so that the adhesive is poor in workability. Furthermore, in the adhesive of the above-mentioned (b2), when the isocyanate group-terminated urethane prepolymer is reacted with a low-molecular-weight diol or diamine, the urethane prepolymer solidifies and then is not melted in some cases and, even when it can be melted, the temperature for melting should be elevated to extremely high temperature, so that the adhesive is poor in workability. The adhesive of the above-mentioned (b3) has disadvantages of high melt viscosity and poor workability and also the deterioration resistance against oleic acid (sweat-deterioration resistance) is not sufficient in many cases depending on specific polyol blend content.